This invention is in the field of sewing machines; more particularly, it is concerned with a needle guard for an industrial lockstitch sewing machine with a rotating looptaker and having the capability for implementing a zigzag stitch.
In sewing machines, it frequently becomes necessary to provide for a needle guard to prevent the looptaker beak from harpooning the sewing needle because of, for example, an operator tugging upon the work material causing the needle to deflect into the path of the looptaker beak. Such hazards are obviated by utilizing a needle guard which prevents movement of the sewing needle towards the looptaker beak. In practice, the needle guard may be fixed with respect to the looptaker beak as is shown in the U.S. Pat. No. 1,155,120, issued on Sept. 28, 1915 to E. B. Allen. In that patent, it is disclosed to provide a needle guard which is part of the rotary looptaker, and which acts to protect the loop seizing beak of the looptaker from contacting the thread carrying needle at substantially the time when the latter is presenting its loop of needle thread to the action of the looptaker. The free edge of the guard in that patent is arranged with respect to the periphery of the looptaker so that during the time the guard is in a position to protect the needle the edge will maintain the uniform relationship with respect to the needle eye during the time that the guard is passing the needle. Alternatively there is the type of needle guard arranged to operate transversely of the line of feed so that an operator tugging upon the work material to advance or retard the feed of work material therethrough will not be successful to deflect the sewing needle into the path of the looptaker beak. Such an arrangement is shown in the Singer 457 Machine in which the needle guard is fashioned at an angle so as to permit a needle already deflected to be led into a position where the looptaker beak may enter a loop of thread immediately behind the sewing needle, without striking the sewing needle. In practice, the needle guard in the 457 Machine is set to a position where it touches a sewing needle without deflecting it while the looptaker beak passes immediately adjacent the needle without touching it. However, in zigzag sewing, particularly for a wide bight zigzag, this adjustment may be made at right needle position and there may be a substantial gap, of approximately, 0.010", between the needle guard and the needle at left needle position due to the lead in angle of the needle guard and vertical displacement of conical pointed portion of the needle in relation to the needle guard surface. In the past it has been possible to provide an improved looptaker having a cobalt tipped beak which would not be blunted by a collision with the sewing needle. However, these special looptakers represent a considerable increase in cost over the usual looptaker, as much as twice the cost thereof.
What is required is some means for protecting the looptaker beak at all positions of the sewing needle, right or left, without the need for resorting to a special and expensive looptaker.